It is proposed that hyperlipoproteinemias could be characterized according to their apolipoprotein concentration and composition. Apolipoprotein rats and monkeys, to demonstrate the difference in apolipoprotein patterns between control and hyperlipoproteinemic animals. The changes in apolipoprotein profiles between hyperlipoproteinemias of different origin will be compared, and the effect of hypolipemic drugs will be studied. The metabolism of the different apolipoproteins will be studied in normal and in pathological conditions. The synthesis and the catabolism of the different apoproteins will be determined; in addition, the apolipoprotein content of peripheral lymph and its physiological implications will be investigated. The development of hyperlipoproteinemia and corresponding changes of apolipoprotein profiles will be correlated with the development of atherosclerosis. The presence of apolipoproteins in the atherosclerotic tissue will be determined and its concentration and flux will be correlated with the serum apolipoproteins.